Image correction processing method and apparatus

Abstract

By using a low-frequency component of attitude data of an uncorrected image resulting from scanning the ground by means of a sensor mounted on a satellite, low-frequency distortion correction coefficients are calculated. By using a high-frequency component of attitude data, a change rate is calculated. From said low-frequency distortion correction coefficients and said change rate, distortion correction coefficients covering a high frequency are calculated. By applying bidirectional resampling to the uncorrected image by using said distortion correction coefficients covering a high frequency, a corrected image is obtained.

What is claimed is: 
     
       1. A correction processing method for processing a digital image signal representing a satellite image including geometric distortion caused by low and high frequency attitude fluctuation and scanning velocity fluctuation comprising the steps of: determining a first set of distortion correction coefficients for a low-frequency component of geometric distortion based on a low-frequency component of attitude data in said image signal;   determining a first deviation quantity on the satellite image corresponding to the attitude fluctuation based on a high-frequency component of attitude fluctuation data and scanning velocity fluctuation data in said image signal;   determining a second set of distortion correction coefficients covering a high frequency component of the geometric distortion by adding signals representing said determined first deviation quantity to a second deviation quantity which corresponds to said first set of distortion correction coefficients; and   correcting the digital image signal representing said satellite image based on said determined second set of distortion correction coefficients.   
     
     
       2. A correction processing method for processing a digital signal representing a satellite image including data dropout caused by reciprocating scanning, comprising: effecting an iteration calculation to correlate an uncorrected image signal resulting from ground scanning witha corrected image signal having geometric distortion corrected while taking the picture element as a unit;   determining whether picture elements correlated with each other in said iteration calculation step are positioned on different scanning lines or not; and   recognizing the occurrence of said data dropout and terminating succeeding iteration calculation operations provided that said picture elements correlated with each other are positioned on different scanning lines.   
     
     
       3. A method for correcting a satellite image having geometric distortion caused by low and high frequency attitude fluctuation and scanning velocity fluctuation using a system having inputting means, outputting means, processing means and memory means, said method comprising the steps of: inputting to said processing means satellite image data stored in said memory means, attitude fluctuation data and scanning velocity fluctuation data by said inputting means;   determining in said processing means a first set of distortion correction coefficients for a low-frequency component of said geometric distortion based on a low-frequency component of said attitude fluctuation data;   determining in said processing means a first deviation quantity on said satellite image corresponding to said attitude fluctuation based on a high-frequency component of said attitude fluctuation data and said scanning velocity fluctuation data;   determining in said processing means a second set of distortion correction coefficients covering a high frequency component of said geometric distortion by adding said first deviation quantity to a second deviation quantity which corresponds to said first set of distortion correction coefficients;   correcting in said processing means said satellite image data having a geometric distortion based on said determined second set of distortion correction coefficients; and   outputting from said processing means said corrected satellite image data by said outputting means.   
     
     
       4. A method according to claim 3 in which said step of correcting said satellite image data comprises bi-directional resampling of said satellite image data based on said second set of distortion correction coefficients. 
     
     
       5. A method according to claim 3 in which said memory means is of a type which includes photographic recording film. 
     
     
       6. An apparatus for correcting a satellite image having geometric distortion caused by low and high frequency attitude fluctuation and scanning velocity fluctuation, comprising: inputting means for inputting satellite image data, attitude fluctuation data and scanning velocity fluctuation data;   processing means for determining a first set of distortion correction coefficients for a low-frequency component of said geometric distortion based on low-frequency components of said attitude fluctuation data inputted by said inputting means, for determining a first deviation quantity on said satellite image corresponding to said attitude fluctuation based on a high-frequency component of said attitude fluctuation data and said scanning velocity fluctuation data inputted by said inputting means, for determining a second set of distortion correction coefficients covering a high frequency component of said geometric distortion by adding said first deviation quantity to a second deviation quantity which corresponds to said first set of distortion correction coefficients, and for correcting said satellite image having the geometric distortion by using said calculated second set of distortion corrrection coefficients; and   memory means for storing said corrected image data.   
     
     
       7. An apparatus according to claim 6, wherein said processing means for correcting said geometric distortion on said satellite image data comprises means for bi-directional resampling of said satellite image data based on said second set of distortion correction coefficients. 
     
     
       8. An apparatus according to claim 6, wherein said memory means includes photographic recording film. 
     
     
       9. A method for correcting a satellite image including data dropout caused by reciprocating scanning, using a system having inputting means, outputting means, processing means and memory means, said method comprising the steps of: inputting to said processing means satellite image data stored in said memory means, attitude fluctuation data and scanning velocity fluctuation data by said inputting means;   effecting iteration calculation, in said processing means, to correlate an uncorrected image resulting from ground scanning with a corrected image having geometric distortion corrected while taking the picture element as a unit;   determining in said processing means, whether or not picture elements correlated with each other in said iteration calculation step are positioned on different scanning lines;   recognizing, in said processing means, the occurrence of said data dropout and terminating succeeding iteration calculation operations provided that said said picture elements correlated with each other are positioned on different scanning lines; and   outputting from said processing means said corrected data excluding said data dropout by said outputting means.